/*

 * json_pack_unpack_fuzzer.cc

 *

 * Fuzz harness for jansson json_unpack() and json_deep_copy() paths.

 * json_unpack() processes a format string + JSON value and extracts

 * typed fields — it involves non-trivial string/type dispatch that

 * is not exercised by the load/dump fuzzer.

 *

 * OSS-Fuzz build: compiled via test/ossfuzz/ossfuzz.sh.

 */

#include <stdint.h>

#include <stddef.h>

#include <string.h>

#include <stdlib.h>

#include "jansson.h"

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)

{

    if (size < 2)

        return 0;

    /* Use first byte to select format variant, rest as JSON input */

    uint8_t variant = data[0] % 8;

    const char *json_str = (const char *)(data + 1);

    size_t json_len = size - 1;

    json_error_t error;

    json_t *root = json_loadb(json_str, json_len,

                               JSON_DECODE_ANY | JSON_ALLOW_NUL, &error);

    if (root == NULL)

        return 0;

    /* Exercise json_deep_copy on whatever we parsed */

    json_t *copy = json_deep_copy(root);

    if (copy != NULL)

        json_decref(copy);

    /* Exercise json_dumps with various flags */

    const int flag_sets[] = {

        0,

        JSON_COMPACT,

        JSON_ENSURE_ASCII,

        JSON_SORT_KEYS,

        JSON_COMPACT | JSON_ENSURE_ASCII,

    };

    int flags = flag_sets[variant % 5];

    char *dumped = json_dumps(root, flags);

    if (dumped != NULL) {

        /* Re-load the dumped output for round-trip check */

        json_t *reparsed = json_loads(dumped, 0, NULL);

        if (reparsed != NULL)

            json_decref(reparsed);

        free(dumped);

    }

    /* Exercise json_unpack with simple format strings if root is an object */

    if (json_is_object(root)) {

        json_t *val = NULL;

        const char *key = NULL;

        /* Unpack first key-value pair */

        void *iter = json_object_iter(root);

        if (iter != NULL) {

            key = json_object_iter_key(iter);

            val  = json_object_iter_value(iter);

            (void)key;

            (void)val;

        }

        /* json_unpack with "o" format — extract object */

        json_t *out_obj = NULL;

        json_unpack(root, "o", &out_obj);

        /* json_unpack with "{s?o}" — optional key lookup */

        json_t *field = NULL;

        json_unpack(root, "{s?o}", "data", &field);

    }

    /* Exercise json_unpack on array */

    if (json_is_array(root) && json_array_size(root) > 0) {

        json_t *first = NULL;

        json_unpack(root, "[o!]", &first);

    }

    json_decref(root);

    return 0;

}